This invention relates to sensor probe assemblies and means for aligning same on opposite sides of a sample chamber.
In sensing of the specific gravity of a biological fluid, such as human urine, it is known to employ sensor probes which are held against or adjacent the sides of a sample chamber at a preselected chamber location. The distance between a pair of probes is not necessarily critical to accuracy for all types of sensing, such as photoelectric sensing shown in U.S. Pat. No. 4,343,316 of Jesperson and entitled "Electronic Urine Flow Monitor". However, when accurate sensing relies upon the speed of conduction of ultrasonic pulses between a pair of transducers, it is critical that such distance remain the same for repeated measurements employing different sample chamber assemblies of possibly different dimension.
It is known to maintain this distance by mounting both the transducers in a stationary fixture. For example, in U.S. Pat. No. 4,418,565 of St. John, entitled "Ultrasonic Bubble Detector", the probes are held fixed on opposite sides of a channel of a probe housing. Flexible tubing conveying the flow being monitored for bubbles conforms to the channel shape when it is pressed into the channel and between the probes fixedly held thereby. The housing defines the channel and thus determines the distance between the probes.
This approach, unfortunately, offers little in the way of a solution when the sensor probes must be movably mounted for relative engagement and disengagement with different sample chambers. In such a system, the probes must be movably mounted between operative sensing positions in which they are engaged with opposite sides of a single chamber to an inoperative position in which they are separated further apart from one another and disengaged from the sampling chamber. It is necessary to be able to reliabily and repeatedly precisely align the sensor probes with different sampling chambers assemblies of possibly different dmensions while still protecting the probe with a suitable housing. Concurrently, the distance between the probes must remain the same for all measurements regardless of dimensional differences between the sampling chambers.